Hydrogenated amorphous silicon (a-SI:H) Is an electronically readable semiconductor material which can be inexpensively deposited over large surface areas. It is a technology under active development within the Xerox Corporation's Palo Alto Research Center (PARC) for a variety of possible applications. Our calculations indicate that, properly designed and properly applied, this material has great promise as a two- dimensionally sensitive electronic sensor for x-ray area detectors, useful in protein crystallography. We are currently making CCD area detectors, which are excellent but are expensive to build and have a much smaller area than we would like. We are impressed by the potential for a-Si:H sensors to solve these problems. We propose therefore to develop large, inexpensive area detectors for protein crystallography, based upon a-Si:H sensors. Xerox Corporation will supply the sensors for this project. Our calculations suggest we can make them large, efficient, fast, high resolution, and with high dynamic range. These deters should be much less expensive to manufacture than CCD-based detectors, their active areas should be comparable to or larger than image phosphor plate detectors, and they will be electronically readable directly into computer systems with speeds of 1 second or faster.